Influence of temperature on the torsional properties of two thermally treated NiTi rotary instruments

Abstract This study aimed to evaluate the influence of temperature on torsional strength and angular deflection of two experimental NiTi rotary instruments manufactured from Blue and Gold thermal treatments and with identical cross-sections. A total of 40 experimental NiTi instruments 25.06 and with a triangular cross-section and manufactured from Blue and Gold thermal treatments were used (n=20). The torsional test was performed in the 3 mm from the tip of the instrument according to ISO 3630-1. The torsional test evaluated the torsional strength and angular deflection to failure at room temperature (21°C ± 1° C) and body temperature (36°C ±1°C). The fractured surface of each fragment was observed by using scanning electron microscopy (SEM). Data were analyzed using an unpaired t test for inter and intra-group comparison and the level of significance was set at 5%. The results showed that the body temperature did not affect the torsional strength and angular deflection of the instruments when compared with room temperature (P>0.05). However, at body temperature, the Blue NiTi instruments presented significantly lower angular deflection in comparison with Gold NiTi instruments (P<0.05). There was no significant difference regarding the torsional strength of the instruments at body temperature (P>0.05). The temperature did not affect the torsional strength of the instruments manufactured from Blue and Gold technology. However, the Blue NiTi instruments presented significantly lower angular deflection than Gold instruments at 36°C temperature.

Resumo O objetivo deste estudo foi avaliar a influência da temperatura nas propriedades de torção (resistência à torção e deflexão angular) de dois instrumentos rotatórios experimentais de NiTi fabricados com secção triangu.ar e tratamentos térmicos Blue e Gold. Quarenta instrumentos experimentais de NiTi 25.06 com tratamento térmico Blue e Gold foram usados (n= 20). Foi avaliada a resistência torcional e a deflexão angular até a fratura na temperatura ambiente (21°C ± 1°C) e corporal (36°C ± 1°C). O teste torcional foi realizado nos 3 mm da ponta dos instrumentos de acordo com a ISO 3630-1. A superfície fraturada de cada instrumento foi observada pelo microscópio eletrônico de varredura (MEV). Os dados foram analisados por meio do teste t não pareado para a comparação inter e intragrupos e o nível de significância à 5%. Os resultados demonstraram que a temperatura corporal não afetou a resistência a torção e deflexão angular quando comparada com a temperatura ambiente (P>0.05). No entanto, na temperatura de 36°C o instrumento com tratamento térmico Blue apresentou menor deflexão angular quando comparado com o Gold (P<0.05). Não houve diferença significante entre os dois instrumentos em relação a resistência à torção. A temperatura corporal não modificou a resistência torcional dos instrumentos fabricados com tecnologia Blue e Gold. No entanto, os instrumentos com NiTi Blue apresentaram menor deflexão angular do que o Gold a 36°C.

CYCLIC AND TORSIONAL FATIGUE RESISTANCE OF THREE DIFFERENT THERMALLY TREATED NICKEL-TITANIUM ROTARY INSTRUMENTS

Background: The aim of this study was to evaluate the cyclic fatigue and torsional fatigue resistance of three thermally treated rotary instruments, such as: Logic 2 25.05 (LOG 25.05), Edge Taper Platinum 25.06 (EDT 25.06) and ProTaper Gold 25.08 (PTG 25.08).Methods: A total of 60 rotary instruments of LOG 25.05, EDT 25.06 and PTG 25.08 were used (n=20). Cyclic fatigue tests were performed at 36°C using an artificial stainless steel canal with a 60ºangle and a 5-mm radius of curvature. The time (in seconds) and number of cycles to fracture (NCF) was recorded. The torsional test evaluated the torque and angle of rotation to failure at 3 mm from the tip according to ISO 3630-1. The fractured surface of each fragment was observed by using scanning electron microscopy (SEM). Data were analyzed using one-way ANOVA and Holm-Sidak's tests for multiple comparison, the level of significance was set at 5%.Results: EDT 25.06 had highest cyclic fatigue resistance (time and NFC), followed by LOG 25.05 and PTG 25.08 (P<0.05). There were no significantly difference between LOG 25.05 and ETP 25.06 regarding the NCF (P>0.05). In relation the torsional test, the LOG 25.05 and ETP 25.06 presented similar torque (P>0.05). The PTG presented greater torque than the other groups (P<0.05). The PTG 25.08 presented the lowest angular rotation to fracture than the other groups (P<0.05). The SEM images demonstrated typical features of cyclic and torsional fracture.Conclusion: In conclusion, the LOG 25.05 and ETP 25.06 presented similar cyclic and torsional properties. The PTG 25.08 showed greater torsional strength.

Antibióticos potencializam a ação antimicrobiana de cimentos endodônticos, em diferentes períodos, após a presa / Antibiotics increase the antimicrobial action of endodontic seal-ers, in different periods, after setting time

O objetivo do presenteestudo foi avaliar a atividade antibacteriana dos cimentos endodôn-ticos MTA Fillapex, Sealapex, Sealer 26 e Endofill puros e acrescidos de amoxicilina e ci-profloxacina frente a duas linhagens ATCC de Enterococcus faecalis (ATCC 29212 e ATCC 4083). Os testes foram realizados pela técnica de difusão radial dos cimentos aplicados di-retamente no ágar e impregnados em discos de papel e pelo teste de contato direto. Para a análise estatística, utilizaram-se os testes de ANOVA e Tukey com nível de significância de 5%. Os resultados mostraram que pela técnica da difusão radial, considerando os cimentos puros, o Sealapex foi o único que apresentou halos de inibição frente às duas linhagens. Já quando da associação de amoxicilina e ciprofloxacina, o MTA Fillapex revelou os melhores halos de inibição para as duas linhagens. Todos os cimentos tiveram a ação potencializada pela adição dos antibióticos (p<0,05). Pela técnica de difusão dos cimentos impregnados em discos de papel, o cimento Sealapex puro fresco demonstrou atividade antimicrobiana em todas as variáveis de tempo. Quando acrescidos dos antibióticos, todos os cimentos ti-veram a ação antimicrobiana potencializada pelas drogas, em todas as variáveis de tempo. Esse mesmo resultado foi observado na técnica do contato direto dos cimentos com ambas as linhagens. A atividade antibacteriana, frente ao E. faecalis, dos cimentos MTA Fillapex, Endofill, Sealer e Sealapex, acrescidos dos antibióticos amoxicilina e ciprofloxacina, foi potencializada mesmo após um longo período da presa dos cimentos.

The objective of this study was to evaluate the antibacterial activity of different endodon-tic cements (MTA Fillapex, Sealapex, Sealer 26, and Endofill), both pure and mixed with 5% of amoxicillin or ciprofloxacin, against two strains of Enterococcus faecalis (ATCC 29212 and ATCC 4083). Bacterial susceptibility testing was conducted by radial diffusion methods and direct contact test after different periods. Data were subjected to ANO-VA and Tukey test with a significance level of 5%. Sealapex was the only pure sealer to promote the inhibition of bacterial growth against both strains in different experimental periods. However, all cements present an increase in antibacterial activity by the addition of antibiotics (p<0.05). MTA Fillapex and Sealapex associated with amoxicillin promoted increased values for bacterial growth against ATCC 29212 and ATCC 4083 in comparison to other groups (p<0.001), including extended periods after setting time. The association of antibiotic agents increased the antibacterial effect of the evaluated sealers against the strains of E. faecalis.